Democrats got some encouraging news on Thursday when liberal billionaire George Soros announced $1.5 million in donations to super PACs supporting President Barack Obama and Democratic congressional candidates.

The contributions, first reported by The New York Times and confirmed by POLITICO, include $1 million to Priorities USA Action, the super PAC devoted to Obama’s reelection and a total of $500,000 to a pair of super PACs devoted to the party’s congressional candidates — Majority PAC and House Majority PAC. It was not immediately clear the precise allocation of the donations between the two, but the Hungarian-born financier had previously donated $175,000 to the latter, including a donation late last month, as well as $100,000 to the latter.

The donations bring to $4.3 million Soros’s total giving this cycle to Democratic outside groups, making him the biggest known donor on the left, but leaving him well short of the $24 million he donated to outside groups ahead of the 2004 election.

After the groups failed to defeat President George W. Bush, Soros expressed leeriness about donating to efforts focused primarily on campaign advertising. So the donations announced Thursday cheered Democrats hoping Soros’s shift would presage similar contributions by like-minded wealthy donors.

Vachon and Democracy Alliance officials did not respond to requests for comment, but the Times reported that other Democracy Alliance members were expected to contribute millions more to the Democratic super PACs.

Don’t expect any cash from Peter Lewis, said a representative for the insurance magnate who, like Soros, donated more than $20 million to Democratic outside groups in 2004 and was among the founding members of the Democracy Alliance.

Though Lewis donated $200,000 to the American Bridge opposition research super PAC, his representative said he is opposed to super PACs that focus on advertising, which is why he dropped out of the Alliance.

Word of Soros’s donation on Thursday also fired up conservatives for whom he is a bogeyman of the same caliber that the new reigning king of outside cash, Sheldon Adelson, is for liberals.

“Here we go again…” began a fundraising email from the Campaign to Defeat Barack Obama, a PAC that has spent $742,000 attacking Obama. Its email asserted Soros’s $1-million donation to Priorities USA will go “to TV ads that are going to smear Mitt Romney in the key battleground states,” and asked for donations to “help us fight back.”